Wednesday, July 23, 2008

Proximal myopathy

The clinical diagnosis of proximal myopathy is usually straightforward. Proximal muscle wasting and weakness is easily demonstratable.

**The weakness is bilateral and usually symmetrical.
**The sensory is always INTACT!

The causes that you need to consider are:
1. Muscular dystrophy
**Duchenne/ Becker muscular dystrophy (look for pseudohypertrophy of calf muscle
** Fascioscapulohumeral dystrophy (look for facial muscle weakness)
**Limb girdle muscular dystrophy

2. Inflammatory muscle disease

** Polymyositis (muscle may be tender)
** Dermatomyositis (Facial heliotrope rash and Gottron's sign)

3. Endocrinopathy
** Cushing's syndrome
** Thyrotoxicosis
** Acromegaly
**ALL will have obvious external features

4. Metabolic myopathies
** Hypo/hyperkalemia, Hypo/hypercalcemia

The above patient with proximal myopathy also has features of Cushing's syndrome. Remember that Cushing's syndrome can cause proximal myopathy but also do not forget that steroid use for polymyositis/dermatomyositis can also cause Cushing's syndrome.

How do you differentiate polymyositis, dermatomyositis and inclusion body myositis ?

Polymyositis Dermatomyositis Inclusion body myositis

Sex F>M F>M M>F

Age Adult Childhood & Adult Elderly > 50 years old

Rash Yes No No

Distribution of weakness Prox > Distal Prox > Distal Prox = Distal,

predilection for

finger/wrist flexion,

knee extensors

CK incr (up to 50x) N or incr (up to 50x) N or mildly incr (<10

x N)

Muscle biopsy amyloid deposits

Response to

immunosupressive Yes Yes No or minimal

EMG myopathic myopathic myopathic/neuropathic


Harry TEOH said...

sorry to ask a question..
do you know are there other websites that are similar as your one in discussing the topic and cases of other speciality, such as surgery, paediatric, orthopaedics and o&g?

i found that such website help me lot in passing my medicine posting...and even now, i am at surgery posting, i still can review and revise back my medicine knowledge..thanks lot

Wuchereria said...

Thanks for the comment !
Not too sure about other specialties.

Anonymous said...

what about similar sites for medicine but on the same level

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